The proposed case-control study will evaluate the efficacy of fecal occult blood screening in reducing colorectal cancer mortality. By employing new methods for case and control selection, this study will provide valid results in a more timely and cost efficient fashion than the two ongoing randomized controlled trials. Approximately 130 deaths attributable to colorectal cancer occurred among members of a prepaid medical care plan (The Greater Marshfield Community Health Plan) during a nine year period. The medical records of these individuals will be reviewed for evidence of early colorectal cancer detection activities. For comparison, the medical records of a random sample of health plan members who are similar in age and sex distribution to the cases will be reviewed as well. Potential confounding factors, such as differences in incidence risk factors and early detection activities other than occult blood testing, will be controlled in the analysis.